BN_CTX_new.3ssl man page
BN_CTX_new, BN_CTX_init, BN_CTX_free — allocate and free BN_CTX structures
#include <openssl/bn.h> BN_CTX *BN_CTX_new(void); void BN_CTX_free(BN_CTX *c);
void BN_CTX_init(BN_CTX *c);
A BN_CTX is a structure that holds BIGNUM temporary variables used by library functions. Since dynamic memory allocation to create BIGNUMs is rather expensive when used in conjunction with repeated subroutine calls, the BN_CTX structure is used.
BN_CTX_new() allocates and initializes a BN_CTX structure.
BN_CTX_free() frees the components of the BN_CTX, and if it was created by BN_CTX_new(), also the structure itself. If BN_CTX_start(3) has been used on the BN_CTX, BN_CTX_end(3) must be called before the BN_CTX may be freed by BN_CTX_free().
BN_CTX_init() (deprecated) initializes an existing uninitialized BN_CTX. This should not be used for new programs. Use BN_CTX_new() instead.
BN_CTX_new() returns a pointer to the BN_CTX. If the allocation fails, it returns NULL and sets an error code that can be obtained by ERR_get_error(3).
BN_CTX_init() and BN_CTX_free() have no return values.
bn(3), ERR_get_error(3), BN_add(3), BN_CTX_start(3)
BN_CTX_new() and BN_CTX_free() are available in all versions on SSLeay and OpenSSL. BN_CTX_init() was added in SSLeay 0.9.1b.